A vector theory of wave scattering from a random medium has been developed using the first-order renormalization theory. It is demonstrated with a chosen anisotropic correlation function that this first-order theory can lead to cross-polarized backscatter when the correlation function of the permittivity fluctuations is not required to have symmetry with respect to the plane of incidence. It is also found that while, in general, 12 modes may exist in the random medium (after excluding the evanescent modes), only two propagating modes are dominant and satisfy the radiation condition. When the correlation function is isotropic in the azimuth, there is no coupling between polarization components, and only one dominant propagating mode may exist for a given incident polarization. Approximate closed form expressions for the scattering coefficients are obtained for the anisotropic correlation function. The effects of anisotropy on the angular behaviors of the scattering coefficients are illustrated.